1. Technical Field
The present invention relates to multicasting and, more particularly, to multicast coding schemes for adapting data signals to transformations imposed by a communication link.
2. Description of the Related Art
Broadcast channel communication is one of the most important classes of the multi-user communication problem, as it models the most widely utilized practical scenario for multiuser downlink transmission. Much effort has been dedicated to researching broadcast channel transmission in the past few decades and some notable progress has been made. Most work regarding broadcast channel communication has focused on the situation in which independent messages are transmitted to the user and less work has focused on the multicast scenario.
Methods for multicasting different messages to different subsets of users are gaining importance due to the increasing demand for multimedia content. This problem is part of the discussions conducted in current standard study groups, such as those directed to the 3GPP LTE-advanced and IEEE 802.16m standards.
Unfortunately, studies on the multicast capacity region of the broadcast channel are scarcer than those related to the capacity region achievable by individual message or unicast transmission. Even for channels such as multiple-input multiple-output (MIMO) Gaussian broadcast channels, where the unicast capacity region has been fully characterized, the multicast capacity region is still an open problem. A notable example is the simple case of a three-user scalar Gaussian channel for which the multicast capacity has not yet been found. Recent works have achieved some developments with regard to transmission capacity under specific conditions.
A deterministic approach for studying wireless networks was introduced relatively recently. This model addresses both broadcast and interference challenges in a wireless network. However, by removing randomness aspects, this model poses some difficult problems, such as finding the network capacity for particular cases in a manner that is analytically tractable.